The use of communication systems through which to communicate data between separate, spaced-apart locations is a necessary adjunct of modern society. A wide variety of different types of communication systems have been developed and are regularly utilized to effectuate communication of data between sending and receiving stations positioned at the separate, spaced-apart locations.
Improvements to existing types of communication systems, as well as implementation of new types of communication systems, have been made possible as a result of advancements in communication technologies. Radio communication systems exemplary of communication systems which have benefited from the advancements in communication technologies. Improvements to existing types, as well as introduction of new types, of radio communication systems have been made possible as a result of the advancements in communication technologies.
A radio communication system inherently permits an increase in communication mobility in contrast to communications effectuated through the use conventional, wireline communication systems. Increased communication mobility is provided as the communication channels defined between the sending and receiving stations of the radio communication systems are defined upon radio links formed therebetween. The communication channels are referred to as radio communication channels and do not require fixed connections between the sending and receiving stations for their formation.
Radio, and other, communication systems are increasingly implemented to utilize digital communication techniques. The use of digital communication techniques permits the communication capacity of a communication system to be increased in contrast to the use conventional, analog techniques. Also, digital communication techniques permit improvement in the quality levels of the communications effectuated in a communication system.
Data which is to be communicated utilizing digital communication techniques is digitized at a sending station. Once digitized, the digitized information is formatted, such as into data packets, and converted into a form to permit its communication upon the communication channel to the receiving station.
In an ideal communication system, the data packets, subsequent to their transmission upon the communication channel and reception at a receiving station, are substantially identical in value to the corresponding data packets prior to their communication upon the communication channel.
Distortion, however, is introduced upon the data during its communication upon a communication channel of an actual communication system. The distortion introduced upon the data causes the values of the data, when received at the receiving station, to differ with the corresponding values of the data packets prior to their communication upon the communication channel. If the amount of distortion is significant, the informational content of the data cannot accurately be recovered at the receiving station.
Multi-path transmission upon the communication channel defined upon the radio link formed between the sending and receiving stations, for instance, causes fading of the data during its communication upon the communication channel. Such fading might alter the values of the symbols of the data, such as the symbols of a data packet, during transmission upon the communication channel. Alteration of the values of the symbols of the data during communication upon the communication channel is referred to as propagation distortion. If the propagation distortion is not properly corrected, the communication quality levels of the communications are, at a minimum, reduced. Various techniques are utilized to compensate for the propagation distortion introduced upon the data as a result of the communication of the data upon a nonideal communication channel.
Increasing the transmit diversity of the data is utilized, for instance, to increase the likelihood that the informational content of the data can be recovered. Time-diversity is a type of transmit diversity. Time-encoding of data, prior to its communication, is referred to as creating time diversity. When the data is time-encoded, the redundancy of the data is increased. Because of the increased redundancy, loss of portions of the data due to fading is less likely to prevent the recovery of the informational content of the data.
Space diversity is also a type of transmit diversity. Space diversity is also utilized to compensate for propagation distortion. Generally, space diversity refers to the utilization of more than one transmit antenna at a sending station at which to transduce the data. The antenna transducers are separated by distances great enough to ensure that the data communicated from the respective transducers fade in an uncorrelated manner. When uncorrelated, fading of the data transmitted upon one communication path to a receiving station is unlikely to fade in the same manner and at the same the time as data communicated to the receiving station upon a different communication path.
Space and time diversity are sometimes utilized together, thereby further to enhance transmission diversity to combat propagation distortion resulting from fading caused by, e.g., multi-path transmission of data. Use of both space and time diversity is referred to as use of space-time diversity.
Space-time codes have been developed, and encoders have been developed to space-time encode the data which is to be communicated to achieve transmit diversity to compensate for communication of the data upon the channels susceptible to fading. And, correspondingly, space-time decoders, operable to decode space-time encoded data at a receiving station have also been developed. Proposals have been set forth, for instance with respect to operational requirements proposed for third-generation cellular communication systems, to provide for multi-data rates services. Such proposals do not permit the use of conventional, space-time coding techniques as, conventionally, variability of coding rates are generally not permitted when conventional, space-time coding techniques are utilized.
An manner by which to provide a space-time code by which to encode data to be communicated upon a channel susceptible to fading which is also permitting of coding at different coding rates is therefore required.
It is in light of this background information related to space-time encoding, and decoding, of data that the significant improvements of the present invention have evolved.